Industry wide practice of wireless baseband signal processing has been generally based on the belief that floating point arithmetic is less economical to build and less power efficient to operate than fixed point arithmetic, even though the fixed point algorithm design process is a tedious and time consuming task that typically requires a significant portion of research and development (R&D) time and investment, which is not needed for floating point calculations.
Wireless communication has now become part of everyone's routine life. Wireless radio links connect mobile phones to the cellular networks, which also connect to the internet, providing basic voice communications and a wide variety of other services such as short messaging, email, internet access and other business applications. The radio coverage of a typical mobile phone application varies from a few hundred meters in small cell applications to 10 kilometers in macro-cell applications in rural areas. At home, people use wireless local area networks, referred to as “WiFi,” that enables portable computing devices such as laptop and smart phones to connect seamlessly to the internet. The coverage of WiFi is up to a hundred meters. Bluetooth is another popular wireless technology with even smaller coverage up to 10 meters, initially intended for wired cable replacement. Bluetooth technology is now widely used in mobile phone for wireless connection between an earpiece and a mobile phone nearby.
These wireless communication systems at each side of the radio link, regardless of coverage sizes, have at least one transmitter antenna and at least one receiver antenna. Typical antenna configurations utilized include receiver diversity (two or more receiving antennas), transmitter beamforming (two or more transmitting antennas), and MIMO (Multiple Input and Multiple Output) (multiple transmitter and receiver antennas).
In mobile phone communications, one side of the communication link is a mobile station while the other side is a base station. In the GSM-based 3GPP family, both GMSK (2G) and EDGE (2.5G) use receiver antenna diversity, while WCDMA (3G) and LTE (4G) use beamforming and/or MIMO. GMSK/EDGE typically involves time division multiple access (TDMA) (physical layer link) technology, WCDMA uses code division multiple access (CDMA) technology, and LTE uses orthogonal frequency division multiple access (OFDMA) technology for the downlink and single channel-frequency division multiple access (SC-FDMA) technology for the uplink. These three different physical link technologies require three quite different baseband signal processing techniques.